1. Field of the Invention
This invention relates to professional turf mowing equipment. More particularly, this invention relates to a new and improved coupling system for permitting the cutting unit of a mower to accurately follow the contours of the ground.
2. Description of Related Art
Mowing machines equipped with multiple cutting units intended for use on golf courses have evolved over the last 40 years reflecting the changing standards of the industry. In general, designs have changed to reflect the increased need for high precision mowing. Currently, there are many designs of coupling systems for attaching the individual cutting units to its parent tractor which allow the cutting units to rotate about one, two, or even three axes for the purpose of accommodating undulating terrain.
In addition, the need for a high quality cut has created the need for a grooved roller which supports the cutting units without excessively laying down the grass. Because a grooved roller has less contact area than a solid roller of equivalent dimensions, its contact areas exert a higher pressure on the turf. Side slippage, or scuffage, becomes a problem with grooved rollers because, as the slippage occurs, the individual segments of the roller pull on the turf. Side slippage is a problem that is well known to people versed in the field.
In conventional mower systems, side slippage can occur as the cutting unit compensates for undulating terrain by pivoting about an axis parallel to the traveling direction. Side slippage occurs with mower systems that do not place this pivot axis substantially coincidental with a point of contact between the cutting unit and the terrain upon which the cutting unit is supported.
Although many mowing devices have been developed that permit a cutting unit to follow the contours of the ground, these mowing devices do not adequately address the problem of side slippage. One example, as shown in U.S. Pat. No. 4,769,976, discloses a linkage for supporting a reel type cutting unit. The linkage provides three degrees of rotation for the cutting unit, allowing it to move independently over uneven terrain. However, the axis, parallel to the direction of travel, around which the cutting unit pivots, is well above ground level. Thus, this structure will cause side slippage.
Another example, as shown in U.S. Pat. No. 5,076,044, is directed to a system that allows the reel mowers in a gang to float and move along the ground in response to variations in the terrain. The reel mowers 30 are suspended by a pair of chains 48 and the reel is driven through a shaft having a pair of U joints, allowing the reel to float and follow the terrain. Again, the axis parallel to the direction of travel, around which the cutting unit pivots, is well above ground level.
Other suspension systems have been developed that create a virtual pivot. One example, as shown in U.S. Pat. No. 5,193,330, is directed to a support system for mower units. FIG. 1 shows an articulating support system that permits a mowing unit to pivot about an axis located below the ground surface using arcuate supports and sliding connections. The arrangement allows a mowing unit 12 to pivot about a pivot axis M transverse to the direction of travel which is below the mowing unit. Mowing unit 12 is suspended by two slide bodies 32 that ride on a curved guide path 31 in the form of a curved slide track. The radius of curvature has its center at point M below the ground surface. The position of the pivot axis M below the ground surface allows the mowing units to unweight the front side to allow easy movement over obstacles. This pivot arrangement is unsuitable to prevent side slippage because the pivot axis is transverse to the direction travel and the pivot axis is located away from ground. Another example, as shown in German Patent No. DE003930811, is directed to a device for matching mowing and cutting to the ground surface and is by the same inventor as the first reference discussed.